1. Field of the Invention
The present invention belongs to the technical field of internal combustion engine, specifically to a two-stroke internal combustion engine.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
A conventional two-stroke internal combustion engine usually includes a cylinder block and a piston. A gas inlet and an exhaust opening of the cylinder block of the conventional two-stroke internal combustion engine are disposed at the lower part of the cylinder wall and close to each other, thus resulting in scavenging short circuit, which means that some air entering the cylinder block is directly exhausted via the exhaust opening, the cylinder performs scavenging insufficiently at the upper part; and some mixed gases are directly exhausted into the atmosphere without combustion, causing technical problems of wasting fuel and generating high-HC (hydrocarbon) waste gas.
The air inlet and the exhaust opening of the conventional two-stroke internal combustion engine are disposed at the bottom of the cylinder wall, so in order to avoid lubricating oil from entering the combustor via the air inlet to result in failure to add the lubricating oil in the crankcase and to lubricate movable components such as the piston and crankshaft, the lubrication mode of adding the lubricating oil special for the two-stroke internal combustion engine into in the fuel oil is employed. However, the lubricating effect is poor; and the life span of the internal combustion engine is shortened. Moreover, participation of the lubricating oil in the combustion results in high-pollutant emission and the combustor tends to generate carbon deposit; meanwhile the piston ring easily gets stuck by the carbon deposit, resulting in gas leak in the combustion engine and further reducing the efficiency of the internal combustion engine.
A patent document with publication No. CN1034247A discloses a technical solution of a two-stroke internal combustion engine. The two-stroke internal combustion engine includes a cylinder head, a cylinder block, an intake valve, an exhaust valve and an oil spray nozzle. The internal combustion engine also includes a protruding portion; the inner wall of the cylinder head is formed with a portion which protrudes toward the combustor; the protruding portion extends along the whole diameter of the inner wall of the cylinder head, and is positioned between an air inlet channel and an air exhaust channel; and the protruding portion separates the air inlet channel from the air exhaust channel. The shielding component is integrally molded with the cylinder head. A spark plug ignites the mixed gas, and the temperature at the end of the combustion is 2,000-2,500 DEG C., so the temperature around the spark plug is higher. The ledges and corners of the shielding component are burnt, and the area around the spark plug is more serious, so the whole cylinder head needs to be replaced after serious burning.
The shielding component is shaped as an inverted triangle. The intake-side plane of the shielding component inclines downward to the exhaust side, the gas entering the cylinder is guided to the lower part of the exhaust side along the intake-side plane of the shielding component, so the fresh air is exhausted in a way of being mixed with the burned waste gas, failing to generate the loop scavenging effect. Meanwhile, the waste gas at the lower part of the intake valve cannot be exhausted, reducing the scavenging effect.
The shielding component is shaped as an inverted triangle. The relatively wide root of the shielding component affects the flame spreading speed, causing a decline to the combustion efficiency.
The shielding component is disposed close to the intake valve, and ⅓ part of the air inlet of the intake valve is shielded, reducing the air inflow effect and the scavenging effect, and causing a decline to the power of the internal combustion engine.
The position and shape of the shield component result in that the combustion starts from one side of the shielding component and then that the flame spreads to the other side of the shielding component. Such combustion mode generates the following results. First, the combustion speed is low; the power and fuel oil efficiency of the internal combustion engine both decline; the internal combustion engine has problems of overheating; the cylinder head, cylinder and piston perform dramatic thermal deformation, which affect the service life. Second, the combustion always starts from one side, and the combustion pressure is not uniform, causing the problem that the piston shakes in the cylinder and the problems of collision between the piston and the cylinder wall and abnormal wearing of the piston and the cylinder wall, and reducing the efficiency and life span of the internal combustion engine. Meanwhile, the shielding component is not uniform in pressure on two sides, so the shielding component needs to be solid, resulting in a relatively large size, a relatively wide root, and occupation of a relatively large area in the combustor of the cylinder head. Therefore, the intake valve and the exhaust valve must be reduced, affecting the exhausting effect. Third, the temperature distribution in the combustor is not uniform, so the cylinder head, the cylinder wall and the piston are not uniformly heated. The temperature at the intake valve is always higher than the temperature on the exhaust side. The cylinder head, the cylinder and the piston are thermally deformed, causing abnormal wear and causing a decline to the power, efficiency and life span.
In order to solve the above technical problems, a four-stroke internal combustion engine is usually adopted. However, the four-stroke internal combustion engine has a complicated structure, and the power density of the four-stroke internal combustion engine is about 50% lower than that the power density of the two-stroke internal combustion engine, so the four-stroke internal combustion engine occupies a large space and has a large weight under the condition of the same power output.